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Nominal Value*Rounded or approximate value of characterizing quantity of a measuring instrument or measuring system that provides guidance for its appropriate use. Examples: a) 1 L as the value marked on a single-mark volumetric flask, b) 100 μL as the setting appearing on the volumeter of a pipette.

Pipette/Pipetter An instrument for transferring a predetermined volume of liquid from one vessel to another. A pipetter is not connected to a reservoir.

Precision* Closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions.

Repeatability* (of Results of Measurements) Measurement precision under a set of repeatability conditions of measurement. Repeatability conditions include:

• the same measurement procedure,

• the same operator/observer,

• the same measuring instrument, used under the same conditions,

• the same location,

• repetition over a short period of time. Comment: for pipetting, variations due to the operator (e.g., cycle time) are to be minimized.

Reproducibility* (of Results of Measurements)Measurement precision under reproducibility conditions of measurement.

SampleThe appropriate representative part of a liquid to be analyzed. The term “test sample“ is used when necessary to avoid confusion with the statistical term “random sample from population”.

Sample CarryoverThe portion of the sample that is retained in the instrument after sample delivery and that may affect subsequent samples.NOTE: Carryover from a positive displacement pipette is less than from an air-displacement pipette.

True valueTrue value is a value that would be obtained by a perfect measurement.

Working rangeTotal volume and temperature range, as well

as ambient conditions, for which instrument performance is specified. Note: do not select volumes outside recommended limits. * Definitions abstracted from

VIM (International Vocabulary of Metrology).

Accuracy*Closeness of agreement between a measured quantity value and a true quantity value of a measurand. Note: “accuracy” is a qualitative concept.

Air CushionAlso called “dead volume”, the air cushion is the volume of air located between the lower part of the pipette piston and the surface level of the sample.

AliquotMeasured portion of a homogeneous entity. A general term referring to multiple samples of any solution, mixture, etc.

DispenserAn instrument for delivering predetermined volumes of liquid from a reservoir. The reservoir may be integrated into the instrument or connected externally.

Measurement Error* Measured quantity value minus a reference quantity value. Comment: this difference or deviation (positive or negative) may be expressed either in the units in which the quantity is measured (absolute error), or as a percentage of the true value (relative error).

Random Error* Component of measurement error that in replicate measurements varies in an unpredictable manner. Notes: 1. Random error is equal to error minus systematic error, 2. Because only a finite number of measurements can

be made, it is possible to determine only an estimate of random error.

Systematic Error*Component of measurement error that in replicate measurements remains constant or varies in a predictable manner. Notes: 1. Systematic error is equal to error minus random error,2. Like true value, systematic error and its causes cannot

be completely known.

Comment: systematic error quantifies the error of accuracy of a pipette.

Good Laboratory Practice Good Laboratory Pratice (GLP) is concerned with the organizational process and the conditions under which laboratory studies are planned, performed, monitored, recorded, and reported.

Measurand*Particular quantity intended to be measured Example: vapor pressure of a given sample of water at 20°C. Note: the specification of a measurand may require statements about quantities such as time, temperature, and pressure.

100

100 µL

Sample

Vmin Vmax

Appendix A: Pipetting Terms

APPENDICES

Air cushion

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Below is an example of how to evaluate the performance of PIPETMAN P10 at 1 μL.

1. Determine the mean value ē of the evaporation loss ei that occurs during your pipetting cycles. Proceed as described in appendix III to determine ei

2. Change the pipette tip and perform the first weighing. Then, keep a regular cycle and perform the 10 following measurements.

Wr = 0.957 mg

W1 = 0.968 mg W6 = 0.966 mg

W2 = 0.960 mg W7 = 0.955 mg

W3 = 0.984 mg W8 = 0.972 mg

W4 = 0.942 mg W9 = 0.958 mg

W5 = 0.969 mg W10 = 0.967 mg

Wr rinsing measurement which is disregarded for the calculation

3. Calculate the mean weight

n: number of weighings

Wi weighing resultsW = (0.968 + 0.960 + 0.984 + 0.942 + 0.969

+ 0.966 + 0.955 + 0.972 + 0.958 + 0.967) / 10

W = 0.964 mg

4. Calculate the mean volumeFor a temperature of 21.5°C and an air pressure of 1013 hPa, the Z factor is equal to 1.0032 μL/mg (see table in Appendix II).

5. Evaluate accuracySystematic error (E):

Relative error (E%):

6. Evaluate precision (repeatability)Standard Deviation (SDw)

Random error (SDv):

Appendix B: Example of a Performance Check Appendix C: Z FactorThe reference calculation equation is: Z = [1/(PW-PA)] [1-(PA/PB)]Where: PA = density of air at t°C.

PW = density of the test liquid at t°C. PB = density of the balance weights. Use 8 g/cc for PB

Values of the conversion factor Z (μL/mg) as a function of temperature and pressure for distilled water.

Temperature °C

AIR PRESSURE HPA

800 853 907 960 1013 106715 1.0018 1.0018 1.0019 1.0019 1.0020 1.0020

15.5 1.0018 1.0019 1.0019 1.0020 1.0020 1.0021

16 1.0019 1.0020 1.0020 1.0021 1.0021 1.0022

16.5 1.0020 1.0020 1.0021 1.0022 1.0022 1.0023

17 1.0021 1.0021 1.0022 1.0022 1.0023 1.0023

17.5 1.0022 1.0022 1.0023 1.0023 1.0024 1.0024

18 1.0022 1.0023 1.0024 1.0024 1.0025 1.0025

18.5 1.0023 1.0024 1.0025 1.0025 1.0026 1.0026

19 1.0024 1.0025 1.0025 1.0026 1.0027 1.0027

19.5 1.0025 1.0026 1.0026 1.0027 1.0028 1.0028

20 1.0026 1.0027 1.0027 1.0028 1.0029 1.0029

20.5 1.0027 1.0028 1.0028 1.0029 1.0030 1.0030

21 1.0028 1.0029 1.0030 1.0030 1.0031 1.0031

21.5 1.0030 1.0030 1.0031 1.0031 1.0032 1.0032

22 1.0031 1.0031 1.0032 1.0032 1.0033 1.0033

22.5 1.0032 1.0032 1.0033 1.0033 1.0034 1.0035

23 1.0033 1.0033 1.0034 1.0035 1.0035 1.0036

23.5 1.0034 1.0035 1.0035 1.0036 1.0036 1.0037

24 1.0035 1.0036 1.0036 1.0037 1.0038 1.0038

24.5 1.0037 1.0037 1.0038 1.0038 1.0039 1.0039

25 1.0038 1.0038 1.0039 1.0039 1.0040 1.0041

25.5 1.0039 1.0040 1.0040 1.0041 1.0041 1.0042

26 1.0040 1.0041 1.0042 1.0042 1.0043 1.0043

26.5 1.0042 1.0042 1.0043 1.0043 1.0044 1.0045

27 1.0043 1.0044 1.0044 1.0045 1.0045 1.0046

27.5 1.0044 1.0045 1.0046 1.0046 1.0047 1.0047

28 1.0046 1.0046 1.0047 1.0048 1.0048 1.0049

28.5 1.0047 1.0048 1.0048 1.0049 1.0050 1.0050

29 1.0049 1.0049 1.0050 1.0050 1.0051 1.0052

29.5 1.0050 1.0051 1.0051 1.0052 1.0052 1.0053

30 1.0052 1.0052 1.0053 1.0053 1.0054 1.0055

W = _

Wi1n

n

i=1∑

NOTE Weights conforming to International Recommendation No. 33 of OIML have been adjusted to give results when weighing in air as if the density of the weights were 8.0 g/mL.

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Half fill the weighing vessel with distilled water.

Cover the weighing vessel with its lid and place it on the balance using a pair of tweezers.

Aspirate a sample.

Tare the balance and take the weighing vessel out of the balance.

Take off the lid with tweezers.

Dispense the sample into a dummy vessel.

Replace the lid on the weighing vessel and, using tweezers, replace the vessel on the balance.

Read the negative result e1 (record the absolute value).

Repeat steps 3 to 8, three times to obtain e2, e3, and e4.

Calculate the evaporation loss ee using the formula:

Under normal conditions, this value is usually between 0.01 mg and 0.03 mg.

Procedure for the Determination of Evaporation Loss.Use the same distilled water, weighing vessel, and balance as you will be using for the gravimetric check.

Product Steel PET Nitril EPDM LCP PA PBT PC PE PVDF TPX POM PP

Acetamide ++ N/A ++ ++ N/A ++ N/A N/A ++ N/A N/A ++ ++

Ethyl acetate ++ + - ++ ++ ++ ++ ++ ++ ++ + N/A ++

Acetone ++ + - ++ ++ ++ ++ - ++ ++ + + ++

Acetonitrile ++ N/A + ++ + N/A N/A - ++ + N/A N/A ++

Acetic acid

20 % ++ ++ + ++ ++ ++ N/A ++ ++ ++ ++ ++ ++

50 % ++ ++ + ++ ++ - N/A + ++ ++ ++ ++ ++

100 % ++ ++ - ++ + - N/A - ++ ++ + + ++

Hydrochloric acid10 % - ++ ++ ++ ++ - ++ ++ ++ ++ ++ ++ ++

20 % - + + ++ ++ - + ++ ++ ++ ++ + ++

37 % - - - ++ ++ - - + ++ ++ ++ - ++

Hydrofluoric acid20 % + + - ++ + - + ++ ++ ++ ++ + ++

40 % - + - ++ - - - + ++ ++ ++ + ++

Formic acid 100 % ++ N/A - ++ ++ - + - ++ ++ N/A + ++

Nitric acid

10 % ++ ++ + ++ ++ - ++ ++ ++ ++ ++ + ++

30 % ++ + - + ++ - + ++ ++ ++ ++ - +

65 % ++ - - - + - - + + + ++ - -

Phosphoric acid20 % ++ N/A + ++ N/A - ++ ++ ++ ++ ++ + ++

85 % ++ N/A - ++ N/A - ++ ++ ++ ++ ++ - ++

Propionic acid50 % ++ - + N/A N/A ++ ++ + ++ ++ N/A - ++

100 % ++ - - N/A N/A + ++ - ++ ++ N/A - ++

Sulfuric acid

20 % ++ ++ + + ++ + ++ ++ ++ ++ ++ + ++

50 % ++ ++ - + ++ - + ++ ++ ++ ++ - ++

95 % ++ + - - - - - + + + ++ - +

Trifluoroacetic acid

20 % ++ N/A - N/A N/A + N/A ++ ++ ++ N/A ++ ++

80 % ++ N/A - N/A N/A - N/A + ++ ++ N/A + ++

100 % ++ N/A - N/A N/A - N/A - ++ ++ N/A - ++

Benzyl alcohol ++ ++ - N/A N/A + N/A - ++ ++ ++ - ++

Aniline ++ - + ++ N/A ++ N/A - + ++ N/A + ++

Butanol / Butyl alcohol ++ ++ ++ ++ N/A ++ ++ ++ ++ ++ N/A ++ ++

Chloroform ++ - - - N/A + - - + ++ + + -

Cyclohexane ++ ++ ++ - N/A ++ N/A ++ ++ - + ++ +

Diacetone alcohol ++ ++ + N/A N/A N/A N/A N/A N/A + N/A N/A ++

Methylene chloride ++ + - - N/A - - - + ++ ++ ++ +

Diethylene glycol ++ N/A ++ ++ ++ N/A N/A N/A ++ ++ ++ ++ ++

Dimethylformamide (DMF) ++ ++ - + ++ ++ ++ - ++ - ++ ++ ++

Dimethylsulfoxide (DMSO) ++ N/A - N/A N/A + N/A - ++ N/A N/A N/A N/A

Dioxane (1,4) ++ ++ - + N/A ++ ++ - ++ + N/A ++ +

Ethanol ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++

Ether ++ ++ ++ + N/A ++ ++ ++ + ++ + ++ ++

Formaldehyde ++ ++ ++ ++ N/A ++ N/A ++ ++ ++ ++ ++ ++

Hexane ++ N/A ++ - + ++ ++ ++ + ++ + ++ ++

Hydrogen peroxide 50 % ++ N/A + ++ N/A ++ ++ ++ ++ ++ ++ ++ ++

Ammonium hydroxide 20 % ++ ++ ++ ++ N/A N/A + - ++ N/A ++ ++ ++

Sodium hydroxide10 % ++ + ++ ++ ++ ++ + - ++ ++ ++ ++ ++

40 % ++ - + ++ ++ ++ + - ++ ++ ++ ++ ++

Sodium hypochlorite 15 % Cl + N/A + ++ ++ ++ ++ ++ ++ ++ ++ - +

Methanol ++ ++ ++ ++ + ++ ++ + ++ ++ ++ ++ ++

Methyl ethyl ketone ++ ++ - + ++ ++ ++ - ++ - + + ++

Pentane ++ N/A ++ - N/A N/A N/A ++ ++ ++ + ++ N/A

Tetrahydrofuran (TH-) ++ ++ + + + ++ + - - + + N/A +

Urea ++ ++ N/A N/A - ++ ++ N/A ++ ++ N/A ++ ++

PET = Polyethylene Terephthalate Nitril = Nitrile EPDM = Ethylene Propylene LCP = Liquid Cristal Polymer PA = Polyamide PBT = Polybutylene Terephthalate PC = Polycarbonate PE = Polyethylene PVDF = Polyvinylidene fluoride

TPX = Polymethylpentene POM = Polyoxymethylene PP = Polypropylene ++ No chemical degradation + Medium resistance to chemical agents - Low resistance to chemical agents N/A No data available

Appendix D: Evaporation Loss Appendix E: Chemical Resistance of Plastics

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51 52APPENDICES | GILSON GUIDE TO PIPETTING GILSON GUIDE TO PIPETTING | USER’S GUIDE

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Question: I have to pipette 100 μL, several pipettes can be used, which one should I choose?

Answer: • According to the properties of the liquid

to be handled, air-displacement or positive-displacement should be chosen.

• P100 is recommended for best precision. P200 can be used, but make sure that specifications are adapted to your protocol.

Question: When should I pre-rinse the tip?

Answer:

Pre-rinsing should be performed:

• every time you change a tip,

• every time you increase the volume setting.

Question: How can I prevent piston corrosion?

Answer: After contact with corrosive liquids, a piston should be cleaned with alcohol and a soft tissue. Take care to avoid shocks or scratches.

Use:

• filter tips,

• corrosion protection kit,

• positive-displacement pipette.

Question: Tips do not fit well. What should I do?

Answer: • Always use Gilson brand tips for Gilson

pipettes.

• Push upward on the tip ejector to make sure it is positioned properly.

• Clean the tip holder with alcohol. If it is worn or has been chemically attacked, order a new part from your Local Gilson representative.

Question: What is accuracy?

Answer:

Closeness of agreement between a measured quantity value and a true quantity value of a measurand. Notes: “accuracy” is a qualitative concept.

Definition abstracted from VIM (International Vocabulary of Metrology).

Question: What is precision?

Answer:

Closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions. Note: Definition abstracted from VIM

(International Vocabulary of Metrology).

Accurate but not precise Precise but not accurate Accurate and precise

FAQ

NOTES

53 NOTES | GILSON GUIDE TO PIPETTING

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